This invention relates to titanium trihalide catalyst systems produced by reduction of a titanium tetrahalide with a magnesium reducing agent.
It is known to reduce titanium tetrahalide with a true Grignard reagent, that is, a compound or mixture of compounds produced by reacting magnesium and an organic halide in the presence of an ether. Such a compound is conventionally expressed as RMgX. It is also known to produce what is termed in the art as "solventless" Grignard, which is produced by reacting magnesium metal with an organic halide in the presence of a solvent which is designated as a non-solvating solvent (i.e., an inert or non-complexing diluent) such as a hydrocarbon as distinguished from an ether.
True Grignard reagents as a practical matter present serious problems as reducing agents in the production of high activity catalysts in view of the difficulty in removing the large amounts of remaining ether which can reduce the effectiveness of such Grignard reagents used in preparing olefin polymerization catalyst systems.
In certain olefin polymerizations, it is necessary to tailor the catalyst to give the type of polymer desired. Particularly in the polymerization of propylene, it is desirable to cause the polymerization to take place in such a manner as to give a stereospecific polymer.